Distillation apparatus



Patented Jan. 6, 1942 DISTILLATION APPARATUS John C. Hecker, Rochester, N. Y., asslgnor to Distillation Products, Inc., Rochester, N. Y., a

corporation of Delaware UNITED STATES PATENT OFFICE the above dimculties.

1 Claim. (Cl. 202.405)

This invention relates to improved high vacuum, unobstructed path distillation apparatus in which the distilland is caused to fiow over the vaporizing surface in the form of a thin film- High vacuum, unobstructed path distillation from thin films is well known in the art. It is also well known that in such distillations, con siderable difiiculty has heretofore been encountered due to' the fact that resinous and carbonaceous materials deposit, on the vaporizing surface. This interrupts the flow of the thin film of distilland and prevents efllcient transfer tilland flows in a thin film. Centrifugal vaporizing surfaces are also employed, the vaporizing surface being rotatable and the distilland being of heat to the film. As a. result, increased decomposition and evolution of gases into the high vacuum apparatus takes place. Heretofore such stills have had to be dismantled for cleaning at the end of relatively short periods of use.

This invention has for its object to overcome Another object is to provide high vacuum, unobstructed path distillation apparatus wherein deposition of solids, resins,

carbonaceous materials, etc., on the vaporizing surface is substantially prevented. A still further object is to provide high vacuum, unobstructed path distillation apparatus which can be operated for substantially longer periods of time without shutdown for cleaning; Another object is to improve the state of the art. Other objects will become apparent from the following description and claim.

These and other objects are accomplished by my invention which includes a high vacuum,

"unobstructed path, thin film still in which the vaporizing surface is coated with aluminum powder, and methods for applying the coating.

4 In the following description, I have given examples illustrating the preferred embodiments of my invention. However, it is to be understood that these are given for the purposes of illustration and not in limitation thereof.

The vaporizing columns in high vacuum, un-

obstructed path stills have heretofore been con- I structed of various metals, such as polished steel, nickel, chromium plated steel and the like.

'The surfaces have been etched to improve the spreading of the distilland or have been spirally corrugated, knurled, etc. The aluminum powder can be applied to all such surfaces in order to improve their characteristics in the manner described.

High vacuum, unobstructed path stills are known in which oppositely facing plates are employed and the distilland flows thereover by gravitational force. Also, it is known to employ' tubular vaporizing surfaces over which the disintroduced onto the approximate center thereof. During operation, the distilland flows by centrifugal force over the rotating surface. My invention is applicable to coated surfaces of these various types.

The aluminum powder is preferably first dispersed in a liquid and is then sprayed or brushed onto the surface. of course, the surface may be immersed, in the dispersion, if it is more convenient to do so. I have found that it is best to employ a volatile organic liquid as a dispersing medium. Examples of satisfactory solvents are amyl acetate and similar esters, and ethyl or methyl alcohol. The dispersion of aluminum powder in such volatile solvents can be applied without difliculty and the volatile solvents quickly volatilize, leaving the aluminum powder deposited on the column. Although non-volatile residues or binders may be present in the mixture of solvent and aluminum powder, I prefer not to use such materials, since they remain on the column and become carbonized during subsequent distillations. A pure aluminum powder in amyl acetate represents a perferred mixture.

If the aluminum powder is applied at ordinary temperatures, it will not firmly adhere to the column and will be more easily removed when the thin film of distilland is passed thereover. I have found that this difliculty can be avoided even though no cement or the like is employed, by merely heating the deposit of alumin powder in air to an elevated temperatui g. This baking process causes the aluminum to become more firmly attached. The cause of the action is not known, since no meltable cements are present and the temperature is not sufficient to melt the aluminum. It is possible that some kind of "eutectic mixture is formed at the interface between the metal of the column and the aluminum particle. The temperature generally employed is about 200 to 375 C. Lower or higher temperatures can, of course, be em- This permits substantially longer runs before a still must be closed down for cleaning. Pumping difliculties and decomposition are considerably decreased. Another outstanding advantage of my invention is that when the stills are eventually dismantled for cleaning, the a1u minum powder coated column can be cleaned with greatease. The deposits can be scrubbed ofl. with little trouble. with 'a brush. Apparently,

the aluminum powder brushes oi! rather easily and does not form a good foundation for the deposited carbonaceous material to'adhere to.

The cleaned column then may be recoated with aluminum powder and put back into use.

What I claim is: a

In a high vacuum, thin film, unobstructed path still provided with vaporizing and condensing surfaces which are separated by substantially unobstructed space, the improvement which comprises-a vaporizing surface which is coated with aluminum powder.

. I JOHN C. BECKER. 

